HAUNTS AND HABITS OF FEA\YS. 3 



5. In some cases there is a tendency to variation in size 

 that cannot be referred to soil or climatic influences. The com- 

 mon grape-fern (Botrychium Virginianuni) will be found in 

 some localities to vary from six inches to two feet in height, all 

 well fruited and matured, and with the extreme sizes growing 

 within a pace of each other in the same soil and with the same 

 environment. The other species of the same genus present 

 similar variations, and judging from size and external appear- 

 ance alone, a regular gradation of forms might be arranged from 

 the most diminutive undivided forms of B. simplex to the larg- 

 est of B. Virginianum. 



6. Another tendency to variation is noticed in the forking 

 of fronds either at the summit or at the ends of the branches. 

 The hart's-tongue (Scolopendriunt) is frequently forked at the 

 summit, the walking-leaf (Camptosorus) less commonly, while 

 the same tendency is noticed in various compound forms, as 

 Asplenium angustifolium, Cheilanthes vestita, Gymnogramme 

 Ehrenbergiana, Dicksonia, Pellcea atropurpurea, and others. 

 Some of the species of Botrychium show the same tendency, 

 especially in their fertile segments. It is probable that all our 

 species will be found to fork under certain conditions. More 

 definite information is desirable with regard to many species 

 that show this tendency, as it doubtless involves the question 

 of ancestry of existing ferns. 



7. In those species whose sterile and fertile fronds are un- 

 like, forms often appear that are intermediate between the ster- 

 ile and fertile fronds, and sometimes even form a graded series 

 from one to the other. This is especially true of the sensitive- 

 fern (Onoclea) and the cinnamon-fern (Osmitnda cinnamomea), 

 and has frequently been the source of so-called "varieties." 

 Whether this variation arises from some peculiarity of environ- 

 ment, or from some inherent tendency to reversion toward an 

 older form, will require more extended observation to deter- 

 mine. One of the varieties of Botrychium ternatum seems to 

 have been founded on a condition which is intermediate in 

 structure between the sterile and fertile segments. 



8. In a few forms there is an apparent mimicry, one species 

 imitating another in foliage or method of fruiting. In the cin- 

 namon-fern just alluded to, which has a cinnamon-colored 



